A ratio between the length and width of a video display unit screen is often called the “aspect ratio”. Conventional aspect ratios for broadcast NTSC video is a ratio of 4:3. However, modern televisions and video display units are often formed with an aspect ratio of 16:9 or even wider. Certain video programs support this wider aspect ratio. However, a large number of legacy programs are still broadcast and/or otherwise available only in the ratio of 4:3.
In certain modern screens, displaying on only part of the screen can cause problems. Specifically, if one part of the screen is used more than others, then that unused part of the screen may age differently than those other parts. In certain screens this can cause uneven brightness, or other problems which make television viewing experience less enjoyable.
Converserly, simply displaying the program on the screen and leaving black bars or like on sides of the displayed program, may look bad.
Some televisions attempt to obviate his problem by allowing the user to widen the program. However, the program recorded at 4:3 ratio (1.25) is then displayed at a 16.9 or other ratio (wider than 1.25). This makes the objects look out of proportion and funny. This has often been found to be acceptable.